The invention relates generally to AC traction motors and more particularly to AC traction motors for locomotives.
Locomotives typically have either a large diesel engine which drives an alternator or are powered by externally supplied electricity. The electrical power from the alternator or external supply is then conducted to traction motors located beneath a platform of the locomotive. The traction motors convert the electrical power to rotational power. The traction motors in turn operatively engage axles to which wheels are attached, and rotate the wheels thereby driving the locomotive.
Traction motors are large electrical motors having the typical motor housing, stator and rotor assembly. Attached to the rotor is a shaft which extends through the housing. Fixedly attached to a pinion end of the shaft is a motor pinion which in turn engages a bull or axle gear for rotating the axle.
At the point where the shaft extends through the housing, the motor includes a drive end bearing assembly. The bearing assembly supports the drive end of the shaft and allows the shaft to rotate relative to the housing. The bearing assembly includes a rotational element such as roller bearings which must be lubricated to limit frictional heating or the bearings will overheat and fail. The bearing assembly also prevents the leakage of lubrication into the interior of the traction motor.
The lubrication of the bearing may be done with different types of lubricating medium. One of the more prevalent types is grease, and the bearings are packed with the grease. It is also known to lubricate the bearings with oil. The use of oil however has several drawbacks. One drawback is that a high static oil level, although insuring an adequate lubricant quantity, results in high viscous losses and high operating temperature. To overcome this drawback, oil feeds are generally employed to circulate a flow of oil through the bearing assembly.
To provide the circulation of oil to the bearing assembly, gravity feeds may be used to eliminate the need for pumps, etc. However, a drawback of using gravity feeds is that there is little pressure generated to force the oil through the oil inlet into the bearing assembly. If the bearing assembly is pressurized relative to the oil supply, the flow of oil into the bearing assembly may be hindered thus preventing the proper flow of oil into the bearing assembly. A lack of sufficient flow may lead to bearing failure.
The cooling of traction motors in locomotive applications also becomes critical in order to maximize or increase the operating life of the traction motor. To cool the motors, blowers are mounted on the locomotive. The blowers pressurize and discharge the pressurized air into a plenum chamber formed within the platform between horizontal upper and lower plates and a pair of vertical I-beams which extend along the sides of the platform and separate the upper or lower plates. Flexible air bellows then connect the interiors of connector ends of the motors to the plenum chamber so that the pressurized air flows into the connector end of the motor.
Air which is introduced into the connector end or commutator end in the case of D.C. Motors, of the motor flows through passageways, formed in the stator and rotor, to the drive end of the motor. As the air flows through the motor, the heat is transferred to the air thereby cooling the motor. The air then flows from the drive end into the environment.
The flow of cooling air from the connector end to the opposite drive end of the motor causes heating of the cooling air before the air reaches the drive end. The heated air may cause the drive end bearing assembly to reach an operating temperature which reduces the period of time the bearing assembly may be operated between maintenance servicing. This reduction of the service period is undesirable.
The flow of air through the passageways also causes a drop in the pressure of the air before the air reaches the drive end of the motor. However, the pressure of the air may still be above the pressure of the oil supply for the bearing assembly at the drive end. This adverse pressure effect is worsened if cooling air is introduced at the drive end.
The pressurized air in the drive end of the motor may cause a small flow of the pressurized air into the drive end bearing assembly. The bearing assembly may then become pressurized relative to the gravity oil feed system. As noted above, this pressurization may hinder the flow of oil into the bearing assembly which is undesirable.
It is therefore an object of the present invention to provide an improved AC traction motor assembly for a locomotive having an oil lubricated bearing assembly for rotatably supporting the drive end of a shaft of the motor.
An additional object of the present invention is to provide an improved AC traction motor having drive end bearing assembly in which the motor and bearing assembly are configured to increase the service life of the bearing assembly.
Yet another object of the present invention is to provide an improved oil feed system to provide a circulation of oil through a drive end bearing assembly for a locomotive traction motor.
A further object of the present invention is to provide an improved drive end sealing assembly which reduces any pressure differential between the supply of an oil feed system and the bearing assembly to reduce any hinderance to the flow of oil into the bearing assembly from the oil feed.